|[AMRadio] Re: Need list of good AM radios to start lookingfor.|
ne1s at neandertech.com
Wed Nov 16 17:12:20 EST 2005
On the Ranger accessory plug are available LV B+ (~300V), HV B+, and each
secondary lead from the mod tranny. You can simply rewire a new plug to hook
the "bottom" of the mod xfmr secondary to LV B+, or, you can do as I did:
mount the plug in an aluminum minibox along with a SPDT switch rated for the
voltages involved to switch the bottom of the mod xfmr secondary between
LVB+ and HV B+. The entire minibox assembly splugs into the acessory plug on
the back of the Ranger. Make sure you ground the minibox to the ground pin
on the accessory plug, for safety's sake.
Works FB, got the idea of using the LV B+ from Timtron.
Ranger puts out ~12-15W of carrier when running the PA on LV B+, perfect for
driving an amp, and no power wasted in a big honking resistor.
John E. Coleman (ARS WA5BXO) writes:
> You are correct of course Jim. I would mount the resistor in its
> own case and construct a cable so as to plug the modulator into the new
> chassis with the resistor and bypass cap, and then the new chassis would
> plug into the Ranger.
> To conserve power and heat, another power supply with lower voltage
> output or variable output would be better. But some time you do with what
> you have and if the 2000 ohm 50 watt resistor is handy and you have an old
> scrap chassis well there you go. I once needed a stiff bias supply so I
> used a single diode and 400 uf filter right off the AC line. Then I placed
> a 100 watt lamp in series with a large variable 100 ohm 100 watt resistor to
> ground. Not a very efficient thing to do but it did hold the bias steady on
> the 805s modulator. This was long before I had access to the HV
> transistors, ETC.
> John, WA5BXO
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